A dual-band filter based on copper-based microfabrication process

Abstract

The application discloses a dual-passband filter based on a copper-based micro-processing technology, which comprises a coaxial outer conductor and a coaxial inner conductor located inside the coaxial outer conductor, an input end feeder and an output end feeder are connected to the coaxial inner conductor, the coaxial inner conductor comprises a first quarter-wavelength transmission line, a second quarter-wavelength transmission line, a first half-wavelength transmission line and a second half-wavelength transmission line, the first quarter-wavelength transmission line and the second quarter-wavelength transmission line are coupled with the first half-wavelength transmission line and the second half-wavelength transmission line at the same time, and the first half-wavelength transmission line and the second half-wavelength transmission line are coupled with each other. The application has the beneficial effects that the transmission loss is small, and the signal shielding property is high.

Description

Technical Field

[0001] The invention belongs to the field of microwave passive devices, and in particular relates to a dual-passband filter based on a copper-based micromachining process. Background Art

[0002] To address the increasingly limited communication spectrum, filters operating in a single frequency band are no longer sufficient to meet new communication requirements. Filters operating in dual or even multi-bands are becoming a research hotspot. With the rapid development of modern microwave and millimeter-wave circuits, the performance requirements of the entire circuit system are becoming increasingly stringent. Millimeter-wave integrated circuits are developing towards miniaturization, high integration, wide frequency bands, low loss, and immunity to radiation. Rectangular micro-coaxial lines, as air-filled metal transmission lines, are suitable for high operating frequencies and offer advantages such as low loss, low crosstalk, and ultra-low dispersion.

[0003] Reference 1 (KSK Yeo and MJ Lancaster, "8-pole high temperature superconductor microstrip dual band bandpass filter design," 2011 IEEE MTT-SInternational Microwave Symposium, Baltimore, MD, USA, 2011, pp. 1-4.) proposes an HTS dual-band bandpass filter. This filter improves isolation by creating a transmission zero between two frequency bands through electromagnetic coupling between two non-adjacent resonators. However, this structure is relatively large.

[0004] Reference 2 (F. Zhang, J. Li, P. Zhao, G. Huang and J. Xu, "A Frequency-Tunable High-Selectivity Dual-Band Bandpass Filter With Independently Controllable Passbands," 2018 International Conference on Microwave and Millimeter Wave Technology (ICMMT), Chengdu, China, 2018, pp. 1-3.) proposes a microstrip structure using a half-wavelength dual-mode resonator loaded by a pair of coupled varactor diodes. This structure independently controls the center frequencies of the two passbands and exhibits high passband selectivity. However, due to the low quality factor of the varactor diodes, this structure suffers from high insertion loss.

[0005] Reference 3 (D. Li, J. -A. Wang, Y. Liu and Z. Chen, "Miniaturized Dual-Band Bandpass Filter With Sharp Roll-Off Using Ring-Loaded Resonator," in IEEE Access, vol. 8, pp. 25588-25595, 2020.) proposes a dual-bandpass filter based on a ring resonator and a 0° feeding structure. Multiple transmission zeros are introduced by utilizing source-load coupling and 0° feeding. However, the center frequencies of this structure are 2.4 GHz and 5.2 GHz, and the operating frequency is relatively low.

[0006] In summary, existing technologies present problems such as large size, low operating frequency, and high loss in dual-band filters. To address the increasingly strained communication spectrum, filters operating in a single frequency band are no longer able to meet new communication requirements. Dual-band and even multi-band filters are becoming a research hotspot. With the rapid development of modern microwave and millimeter-wave circuits, the performance requirements for the entire circuit system are becoming increasingly stringent. Millimeter-wave integrated circuits are developing towards miniaturization, high integration, wide frequency bands, low loss, and immunity to radiation. Rectangular micro-coaxial lines, as air-filled metal transmission lines, are suitable for high operating frequencies and offer advantages such as low loss, low crosstalk, and ultra-low dispersion. Summary of the Invention

[0007] The object of the present invention is to provide a dual-passband filter based on a copper-based micromachining process.

[0008] To achieve the above object, the present invention provides the following technical solutions:

[0009] A dual-passband filter based on a copper-based micromachining process includes a coaxial outer conductor and a coaxial inner conductor located inside the coaxial outer conductor. The coaxial inner conductor is connected to an input feeder and an output feeder. The coaxial inner conductor includes a first quarter-wavelength transmission line, a second quarter-wavelength transmission line, a first half-wavelength transmission line, and a second half-wavelength transmission line. The first quarter-wavelength transmission line and the second quarter-wavelength transmission line are simultaneously coupled to the first half-wavelength transmission line and the second half-wavelength transmission line. The first half-wavelength transmission line and the second half-wavelength transmission line are coupled to each other.

[0010] Preferably, the coaxial outer conductor adopts a rectangular micro-coaxial five-layer process design in its height direction, each layer has the same height and the coaxial inner conductor is located in the third layer process of the coaxial outer conductor.

[0011] Preferably, the first quarter wavelength transmission line and the second quarter wavelength transmission line are connected by a short-circuit ground line, the first half wavelength transmission line and the second half wavelength transmission line are both zigzag bent, the first half wavelength transmission line is connected with the input end feed line, and the second half wavelength transmission line is connected with the output end feed line.

[0012] Preferably, the first half wavelength transmission line and the second half wavelength transmission line are symmetrically arranged and the openings of the two zigzags face each other, and the first quarter wavelength transmission line and the second quarter wavelength transmission line are located inside the two openings.

[0013] Preferably, the input end feed line and the output end feed line both have an impedance of 50 ohms.

[0014] Preferably, a plurality of rectangular release holes are formed on the inner side wall and the outer side wall of the coaxial outer conductor at intervals.

[0015] Preferably, a plurality of dielectric support strips for fixing the coaxial inner conductor are arranged on the coaxial outer conductor below the coaxial inner conductor.

[0016] The present application has the advantages that: the present application adopts a copper-based micro-processing technology, compared with the commonly used planar PCB technology, the planar transmission line has higher transmission loss in the high frequency band, while the micro coaxial line has small insertion loss, and the high frequency advantage is particularly obvious, and the signal shielding property is high. A plurality of transmission zeros are introduced by using source-load coupling, and the out-of-band suppression capability is strong. The three-dimensional structure is obtained by using the copper-based micro-processing technology, which is convenient for three-dimensional integrated processing and integration of the device, and the size is small and the precision is high, which is micron level. BRIEF DESCRIPTION OF DRAWINGS

[0017] Figure 1 is a structural schematic diagram of the present application.

[0018] Figure 2 is a side view of the present application.

[0019] Figure 3 is a top view of the present application.

[0020] Figure 4 is a structural size schematic diagram of Figure 3 .

[0021] Figure 5 is an S parameter simulation curve diagram of the present application.

[0022] Among them: 1. Coaxial outer conductor; 2. Coaxial inner conductor; 21. First quarter-wavelength transmission line; 22. Second quarter-wavelength transmission line; 23. First half-wavelength transmission line; 24. Second half-wavelength transmission line; 3. Input feed line; 4. Output feed line; 5. Dielectric support bar; 6. Ground wire; 7. Rectangular release hole. DETAILED DESCRIPTION

[0023] The technical solution of this patent is further described in detail below in conjunction with specific implementation methods.

[0024] like Figures 1 to 4 As shown, a dual-passband filter based on a copper-based micromachining process according to the present invention includes a coaxial outer conductor 1 and a coaxial inner conductor 2 located within the coaxial outer conductor 1. The coaxial inner conductor 2 is connected to an input feed line 3 and an output feed line 4. The coaxial inner conductor 2 includes a first quarter-wavelength transmission line 21, a second quarter-wavelength transmission line 22, a first half-wavelength transmission line 23, and a second half-wavelength transmission line 24. The first quarter-wavelength transmission line 21 and the second quarter-wavelength transmission line 22 are simultaneously coupled to the first half-wavelength transmission line 23 and the second half-wavelength transmission line 24, and the first half-wavelength transmission line 23 and the second half-wavelength transmission line 24 are coupled to each other. Both the coaxial inner conductor 2 and the coaxial outer conductor 1 are made of copper, which has good conductivity and low loss during signal transmission. The coaxial outer conductor 1 covers the outside of the coaxial inner conductor 2 to shield electromagnetic interference. The first half-wavelength transmission line 23 and the second half-wavelength transmission line 24 are coupled to each other, and the first quarter-wavelength transmission line 21 and the second quarter-wavelength transmission line 22 are simultaneously coupled to the first half-wavelength transmission line 23 and the second half-wavelength transmission line 24 to effectively filter out frequencies outside the specific frequency point.

[0025] The coaxial outer conductor 1 adopts a rectangular micro-coaxial five-layer process design in its height direction, with each layer having the same height and the coaxial inner conductor 2 located in the third layer of the coaxial outer conductor 1; compared with the traditional planar PCB process, this structure has low transmission loss in the high frequency band.

[0026] The first quarter-wavelength transmission line 21 and the second quarter-wavelength transmission line 22 are connected by a short-circuit grounding line 6, and the first half-wavelength transmission line 23 and the second half-wavelength transmission line 24 are both bent in an "X" shape. The first half-wavelength transmission line 23 is connected to the input end feeder 3, and the second half-wavelength transmission line 24 is connected to the output end feeder 4; through the "X" shape design, the phase area between the first quarter-wavelength transmission line 21 and the first half-wavelength transmission line 23 and the relative area between the second quarter-wavelength transmission line 22 and the second half-wavelength transmission line 24 are increased.

[0027] The first half-wavelength transmission line 23 and the second half-wavelength transmission line 24 are symmetrically arranged and the two V-shaped openings face each other, and the first quarter-wavelength transmission line 21 and the second quarter-wavelength transmission line 22 are located inside the two openings.

[0028] The impedance of the input end feeder 3 and the output end feeder 4 is 50 ohms, which can meet the maximum power transmission and the minimum loss at the same time, and the system impedance of 50 ohms is also matched with the impedance of the quarter-wavelength and the port of the transmission line, so that the reflection loss is small.

[0029] The inner side wall and the outer side wall of the coaxial outer conductor 1 are both provided with a plurality of rectangular release holes 7 at intervals, and the rectangular release holes 7 can balance the air pressure inside and outside the coaxial outer conductor 1.

[0030] The coaxial outer conductor 1 is provided with a plurality of dielectric support strips 5 located below the coaxial inner conductor 2 for fixing the coaxial inner conductor 2, and the dielectric support strips 5 are made of insulating materials such as ceramic and the like.

[0031] Compared with the common plane PCB process, the plane transmission line has higher transmission loss in the high frequency band, the micro coaxial line has small insertion loss, the advantage is particularly obvious in the high frequency, and the signal shielding property is high. The three-dimensional structure manufactured by using the rectangular micro coaxial process is convenient for three-dimensional integrated processing and integration of the device, and the size is small and the precision is high, which is micron level. At the same time, a plurality of transmission zeros are introduced by using source-load coupling, and the out-of-band suppression ability is strong. In addition, the filter has simple and compact structure, good out-of-band suppression ability and small loss, and has good application prospect in modern wireless communication system.

[0032] The size specifications of the present application are as shown in Figure 5 The horizontal area of the present application is 5.388*3.472mm², the 5-layer process design is adopted, the height of each layer is the same, the total height is 0.5mm, the inner conductor width is 0.195mm, and the height is 0.1mm. Figure 4 , 5 The size parameters of the dual-passband filter are as follows: W1=0.19mm, W2=0.13mm, Wp=0.195mm, gap=0.135mm, gap1=0.1mm, Ls=0.16mm, Lp=0.3mm, L1=0.73mm, L2=2.07mm, L3=0.8mm, n=0.712mm, n1=0.53mm, m=0.14mm, s=0.074mm.

[0033] The present invention is modeled and simulated in the electromagnetic simulation software Ansys Electronics Desktop 2022R1, as shown in Figure 5 As shown in the figure, the passband center frequencies of the dual-passband filter are 20.6 GHz and 29.44 GHz respectively, the in-band return losses are better than 20.31 dB and 22.29 dB respectively, and the insertion losses are less than 0.91 dB and 0.68 dB respectively. The two zeros outside the passband at 17.53 GHz and 22.87 GHz improve the out-of-band suppression capability of the dual-passband filter.

[0034] It will be apparent to those skilled in the art that the present invention is not limited to the details of the exemplary embodiments described above and that the invention can be embodied in other specific forms without departing from the spirit or essential characteristics of the invention. Therefore, the embodiments should be considered in all respects as illustrative and non-restrictive, and the scope of the invention is defined by the appended claims, not the foregoing description, and all variations within the meaning and range of equivalents of the claims are intended to be included therein. Any reference sign in a claim should not be construed as limiting the claim to which it relates.

[0035] In addition, it should be understood that although this specification is described in terms of implementation methods, not every implementation method contains only one independent technical solution. This narrative method of the specification is only for the sake of clarity. Those skilled in the art should regard the specification as a whole. The technical solutions in each embodiment can also be appropriately combined to form other implementation methods that can be understood by those skilled in the art.

Claims

1. A dual-passband filter based on copper-based micromachining technology, characterized by: The invention comprises a coaxial outer conductor (1) and a coaxial inner conductor (2) located inside the coaxial outer conductor (1); an input end feed line (3) and an output end feed line (4) are connected to the coaxial inner conductor (2); the coaxial inner conductor (2) comprises a first quarter wavelength transmission line (21), a second quarter wavelength transmission line (22), a first half wavelength transmission line (23) and a second half wavelength transmission line (24); the first quarter wavelength transmission line (21) and the second quarter wavelength transmission line (22) are coupled to each other; the first quarter wavelength transmission line (21) and the first half wavelength transmission line (23) are coupled to each other; the second quarter wavelength transmission line (22) and the second half wavelength transmission line (24) are coupled; and the first half wavelength transmission line (23) and the second half wavelength transmission line (24) are coupled to each other; The first quarter-wavelength transmission line (21) and the second quarter-wavelength transmission line (22) are connected via a short-circuit grounding line (6); the first half-wavelength transmission line (23) and the second half-wavelength transmission line (24) are both bent in a "J" shape; the first half-wavelength transmission line (23) is connected to the input end feeder (3); and the second half-wavelength transmission line (24) is connected to the output end feeder (4); The first half-wavelength transmission line (23) and the second half-wavelength transmission line (24) are symmetrically arranged, and the two X-shaped openings face each other, and the first quarter-wavelength transmission line (21) and the second quarter-wavelength transmission line (22) are located inside the two openings.

2. The dual-passband filter based on copper-based micromachining technology according to claim 1, characterized in that: The coaxial outer conductor (1) is designed using a rectangular micro-coaxial five-layer process in its height direction, each layer has the same height, and the coaxial inner conductor (2) is located in the third layer of the coaxial outer conductor (1).

3. The dual-passband filter based on copper-based micromachining technology according to claim 1, characterized in that: The impedance of the input end feeder (3) and the output end feeder (4) are both 50 ohms.

4. The dual-passband filter based on copper-based micromachining technology according to claim 1, characterized in that: A plurality of rectangular release holes (7) are provided at intervals on the outer side wall of the coaxial outer conductor (1).

5. The dual-passband filter based on copper-based micromachining technology according to claim 1, characterized in that: The dielectric support strip (5) is inserted into the third layer of the coaxial outer conductor (1), and the lower surface of the dielectric support strip (5) is flush with the lower surface of the coaxial inner conductor (2), and is used to fix the coaxial inner conductor (2).

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